3-Heteroaryl-3,5-dihydro-4-oxo-4H-pyridazino[4,5-B]indole-1-carboxamide Derivatives, Their Preparation and Therapeutic Use

ABSTRACT

A subject-matter of the invention is the compounds of general formula (I) 
     
       
         
         
             
             
         
       
     
     in which X represents a hydrogen or halogen atom;
 
R 1  represents a hydrogen atom or a (C 1 -C 4 )alkyl group; R 2  and R 3  each represent, independently of one another, a hydrogen atom or a (C 1 -C 4 )alkyl group or else R 2  and R 3  form, with the nitrogen atom which carries them, a pyrrolidinyl, piperidinyl, morpholinyl or 4-alkylpiperazinyl group; and Het represents a heteroaromatic group of pyridinyl, 1-oxidopyridinyl, quinolinyl, isoquinolinyl, pyrimidinyl, pyrazinyl or pyridazinyl type, it being possible for the heteroaromatic group to carry one or more halogen atoms and/or one or more (C 1 -C 4 ) alkyl or (C 1 -C 4 ) alkoxy groups; in the form of bases, of addition salts with acids, of solvates or of hydrates, the pharmaceutical compositions comprising them, processes for their preparation and synthetic intermediates.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 11/427,508,filed Jun. 29, 2006, now allowed, which is a continuation of U.S.application Ser. No. 10/499,725, filed Jun. 21, 2004, now U.S. Pat. No.7,109,194 BE, issued, Sep. 19, 2006, which was the National Stage ofInternational application No. PCT/FR2002/03,979, filed Nov. 20, 2002,all of which are incorporated herein by reference in their entirety;which claims the benefit of priority of French Patent Application No.01/16,701, filed Dec. 21, 2001.

A subject-matter of the invention is compounds derived from3-heteroaryl-3,5-dihydro-4-oxo-4H-pyridazino[4,5-b]indole-1-carboxamide.

Compounds derived from 3,5-dihydropyridazino-[4,5-b]indole, disclosed inthe document WO-A-00/44751, are already known, which compounds have anin vitro affinity for peripheral-type benzodiazepine receptors (PBR or psites).

There still exists a need to find and develop products exhibiting a goodin vivo activity.

The invention meets this target by providing novel compounds whichexhibit an in vitro and in vivo affinity for peripheral-typebenzodiazepine receptors.

A first subject-matter of the invention relates to the compoundscorresponding to the general formula (I) below.

Another subject-matter of the invention relates to processes for thepreparation of the compounds of general formula (I).

Another subject-matter of the invention relates to compounds which canbe used in particular as intermediates in the synthesis of the compoundsof general formula (I).

Another subject-matter of the invention relates to the uses of thecompounds of general formula (I), in particular in medicaments or inpharmaceutical compositions.

The compounds of the invention correspond to the general formula (I):

in whichX represents a hydrogen or halogen atom,R₁ represents a hydrogen atom or a (C₁-C₄)alkyl group,R₂ and R₃ each represent, independently of one another, a hydrogen atomor a (C₁-C₄)alkyl group or else R₂ and R₃ form, with the nitrogen atomwhich carries them, a pyrrolidinyl, piperidinyl, morpholinyl or4-alkylpiperazinyl group, andHet represents a heteroaromatic group of pyridinyl, 1-oxidopyridinyl,quinolinyl, isoquinolinyl, pyrimidinyl, pyrazinyl or pyridazinyl type,it being possible for the heteroaromatic group to carry one or morehalogen atoms and/or one or more (C₁-C₄)alkyl or (C₁-C₄)alkoxy groups.

In the context of the present invention:

-   -   a (C₁-C₄)alkyl group represents a saturated and linear or        branched aliphatic group comprising 1 to 4 carbon atoms. Mention        may be made, by way of examples, of the methyl, ethyl, propyl,        isopropyl, butyl, isobutyl or tert-butyl groups.    -   a (C₁-C₄)alkoxy group represents an oxygen radical substituted        by an alkyl group comprising from 1 to 4 carbon atoms as defined        above.

Preferred compounds according to the invention are the compounds forwhich

X represents a halogen atom; and/orR₁ represents a (C₁-C₄)alkyl; and/orR₂ and R₃ each represent, independently of one another, a hydrogen atomor a (C₁-C₄)alkyl group, more particularly a methyl or an ethyl, or elseR₂ and R₃ form, with the nitrogen atom which carries them, apyrrolidinyl, piperidinyl, morpholinyl or 4-alkylpiperazinyl group;and/orHet represents a heteroaromatic group of pyridinyl, quinolinyl,isoquinolinyl, pyrimidinyl, pyrazinyl or pyridazinyl type which cancarry one or more halogen atoms, more particularly a bromine atom,and/or one or more (C₁-C₄)alkyl groups, more particularly a methyl, or(C₁-C₄)alkoxy groups, more particularly a methoxy.

Compounds for which X, R₁, R₂, R₃ and Het simultaneously are as definedabove in the subgroups of preferred compounds are particularly preferredand more specifically, among these, the compounds for which:

X represents a chlorine atom and R₁ represents a methyl group.

By way of example, compounds of the invention are the following:

-   1:    7-fluoro-N,N,5-trimethyl-4-oxo-3-(pyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   2:    7-fluoro-N,N,5-trimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   3:    7-fluoro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide    hydrochloride (1:1)-   4:    7-fluoro-N,N,5-trimethyl-4-oxo-3-(2-methoxypyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   5:    7-fluoro-N,N,5-trimethyl-4-oxo-3-(quinolin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   6:    1-[[7-fluoro-5-methyl-3-(pyrimidin-2-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]-pyrrolidine-   7:    4-methyl-1-[[7-fluoro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]piperazine    hydrochloride (1:1)-   8:    1-[[7-fluoro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]-pyrrolidine-   9:    7-fluoro-N,5-dimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   10:    7-fluoro-5-methyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   11:    7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   12:    7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide    hydrochloride (1:1)-   13:    7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   14:    7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide    hydrochloride (1:1)-   15:    7-chloro-N,N,5-trimethyl-4-oxo-3-(5-methylpyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   16:    7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methoxypyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   17:    7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methylpyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   18:    7-chloro-N,N,5-trimethyl-4-oxo-3-(2-bromopyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   19:    7-chloro-N,N,5-trimethyl-4-oxo-3-(quinolin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   20:    7-chloro-N,N,5-trimethyl-4-oxo-3-(isoquinolin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   21:    7-chloro-N,N,5-trimethyl-4-oxo-3-(6-methyl-pyridazin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   22:    7-chloro-N,N,5-trimethyl-4-oxo-3-(pyrimidin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   23:    7-chloro-N,N,5-trimethyl-4-oxo-3-(pyrimidin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   24:    7-chloro-N,N,5-trimethyl-4-oxo-3-(pyrazin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   25:    1-[[7-chloro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]-pyrrolidine    hydrochloride (1:1)-   26:    4-methyl-1-[[7-chloro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]piperazine    hydrochloride (1:1)-   27:    1-[[7-chloro-5-methyl-3-(pyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]-pyrrolidine-   28:    7-chloro-N,5-dimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   29:    7-chloro-5-methyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   30:    7-chloro-N,N,5-trimethyl-4-oxo-3-(4-methoxypyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   31:    1-[[7-chloro-5-methyl-3-(pyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]morpholine-   32:    7-chloro-N,N,-diethyl-5-methyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   33:    7-chloro-N-ethyl-N,5-dimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   34:    1-[[7-chloro-5-methyl-3-(pyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]-piperidine-   35:    7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methylpyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   36:    1-[[7-chloro-5-methyl-3-(2-methylpyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidine-   37:    7-chloro-N,N,5-trimethyl-3-(1-oxidopyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   38:    7-chloro-3-(2-methoxypyridin-4-yl)-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide-   39:    3-(2-bromopyridin-4-yl)-7-chloro-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide

The compounds of the invention can exist in the form of bases, ofaddition salts with acids, of solvates or of hydrates.

The compounds of general formula (I) can be prepared by the processesillustrated subsequently.

Throughout the continuation of the description, the intermediatecompounds (II), (III), (IV) and (V) are those presented in the schemebelow.

According to a first preparation route, a compound of general formula(II), in which X and R₁ are as defined above and R′ and R″ eachrepresent, independently of one another, a (C₁-C₄)alkyl group, istreated with a heteroarylhydrazine in a polar solvent in the presence ofacid at the reflux temperature, in order to obtain an ester of generalformula (III) in which X, R₁, Het and R″ are as defined above.

This ester is converted to the amide of general formula (I) by reactionwith an amine of general formula HNR₂R₃, in which R₂ and R₃ are asdefined above, for example in the presence of a trialkylaluminumderivative in a solvent such as toluene, or else by saponification ofthe ester of general formula (III) to the acid, using, for example,lithium hydroxide in a mixture of methanol, water and an etherealsolvent, and then by coupling the acid obtained, according to methodsknown to a person skilled in the art, with an amine of general formulaHNR₂R₃ as defined above.

According to a second preparation route, a diester of general formula(II) is treated with hydrazine by heating in a solvent, such as aceticacid or toluene, in the presence of acid, in order to obtain an ester ofgeneral formula (IV) in which X, R₁ and R″ are as defined above.

This ester is converted to the amide of general formula (V), in which X,R₁, R₂ and R₃ are as defined above, by reaction with an amine of generalformula HNR₂R₃, in which R₂ and R₃ are as defined above, for example inthe presence of a trialkylaluminum derivative in a solvent such astoluene.

Finally, an N-heteroarylation is carried out by a coupling reaction inthe presence of a heteroaryl halide or else of a heteroarylboronic acidderivative and of a metal salt, such as a copper salt, resulting in acompound of general formula (I).

This N-heteroarylation reaction can also be carried out on the compoundof general formula (IV) to result in the ester of general formula (III).This ester is finally converted to the amide of general formula (I) byreaction with an amine of general formula HNR₂R₃, in which R₂ and R₃ areas defined above, for example in a mixture of solvents, such as, inparticular, dichloromethane and methanol.

The amides of general formulae (V) and (I) can also be obtained bysaponification of the esters of respective general formulae (IV) and(III) to the acids and by then coupling the acids obtained with an amineof general formula HNR₂R₃, as defined above, according to methods knownto a person skilled in the art.

The boronic acid derivatives carrying a heteroaromatic group arecommercially available or can be prepared by methods analogous to thoseknown in the literature (Synth. Commun., 1996, 26, 3543 and Li et al.,J. Med. Chem., 1995, 38, 4570).

The compounds of general formula (I) for which X, R₁, R₂ and R₃ are asdefined above and for which Het represents a heteroaromatic group of1-oxidopyridinyl type can be prepared by oxidation, using an oxidizingagent such as hydrogen peroxide, of the equivalent derivative for whichHet represents a heteroaromatic group of pyridinyl type.

The compounds of general formula (I) for which X, R₁, R₂ and R₃ are asdefined above and for which Het represents a heteroaromatic group of2-halopyridinyl type can be prepared by halogenation, using a phosphorustrihalide, for example, of the equivalent derivative for which Hetrepresents a heteroaromatic group of 1-oxidopyridinyl type.

The compounds of general formula (I) for which X, R₁, R₂ and R₃ are asdefined above and for which Het represents a heteroaromatic group of2-alkoxypyridinyl type can be prepared by substitution, by means of asodium alkoxide, for example, of the equivalent derivative for which Hetrepresents a heteroaromatic group of 2-halopyridinyl type.

The preparation of the starting compounds of general formula (II) isdisclosed in the document WO-A-00/44751 in the case where X is achlorine atom. This preparation method is employed analogously when X isa fluorine atom.

Another subject-matter of the invention relates to the compounds ofgeneral formula (II)

in whichR₁ represents a hydrogen atom or a (C₁-C₄)alkyl group,R′ and R″ each represent, independently of one another, a (C₁-C₄)alkylgroup, of use as synthetic intermediates in the preparation of thecompounds of general formula (I).

Another subject-matter of the invention relates to the compounds ofgeneral formula (III)

in whichX represents a hydrogen or halogen atom,R₁ represents a hydrogen atom or a (C₁-C₄)alkyl group,Het represents a heteroaromatic group of pyridinyl, quinolinyl,isoquinolinyl, pyrimidinyl, pyrazinyl or pyridazinyl type, it beingpossible for the heteroaromatic group to carry one or more halogen atomsand/or one or more (C₁-C₄)alkyl or (C₁-C₄)alkoxy groups,R″ represents a (C₁-C₄)alkyl group,of use as synthetic intermediates in the preparation of the compounds ofgeneral formula (I).

Another subject-matter of the invention relates to the compounds ofgeneral formula (IV)

in whichX represents a hydrogen or halogen atom,R₁ represents a hydrogen atom or a (C₁-C₄)alkyl group,R″ represents a (C₁-C₄)alkyl group,of use as synthetic intermediates in the preparation of the compounds ofgeneral formula (I).

Another subject-matter of the invention relates to the compounds ofgeneral formula (V)

in whichX represents a hydrogen or halogen atom,R₁ represents a hydrogen atom or a (C₁-C₄)alkyl group,R₂ and R₃ each represent, independently of one another, a hydrogen atomor a (C₁-C₄)alkyl group or else R₂ and R₃ form, with the nitrogen atomwhich carries them, a pyrrolidinyl, piperidinyl, morpholinyl or4-alkylpiperazinyl group,of use as synthetic intermediates in the preparation of the compounds ofgeneral formula (I).

Other compounds are novel and of use as synthetic intermediates in thepreparation of the compounds of general formula (I). They are thecompounds of general formulae (III) and (IV) above in which R″ no longerrepresents a (C₁-C₄)alkyl group but a hydrogen atom.

The examples which follow illustrate the preparation of some compoundsof the invention. The elemental microanalyses and the IR and NMR spectraconfirm the structures of the compounds obtained.

EXAMPLE 1 Compound No. 17-Fluoro-N,N,5-trimethyl-4-oxo-3-(pyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide1.1. Potassium 2-(4-fluoro-2-nitrophenyl)-1-methoxy-carbonylethenolate

47 g (0.419 mol) of potassium t-butoxide are introduced into 900 ml oftetrahydrofuran. The reaction medium is cooled to approximately −5° C.and 90 ml of methanol are added. 61.2 g (0.419 mol) of ethyl oxalate aresubsequently introduced. A solution of 54 g (0.348 mol) of4-fluoro-2-nitrotoluene in 100 ml of tetrahydrofuran is then addeddropwise at low temperature. Stirring is maintained for 12 h at ambienttemperature. The solution is filtered. The solid obtained is washed withdiethyl ether and dried under reduced pressure.

78 g of a purple solid formed of potassium2-(4-fluoro-2-nitrophenyl)-1-methoxycarbonylethenolate are obtained,comprising from 10 to 20% of potassium2-(4-fluoro-2-nitrophenyl)-1-ethoxycarbonylethenolate.

1.2. Methyl 6-fluoro-1H-indole-2-carboxylate

A mixture of 35 g of potassium salt obtained in stage 1.1. in 500 ml ofethanol is cooled to approximately 0° C. 80 ml of concentratedhydrochloric acid are added in small portions. 35 g (627 mmol) of ironpowder are also added portionwise. The mixture is heated at reflux for 5h and then cooled and filtered. The solid obtained is rinsed withdichloromethane. The filtrate is concentrated under reduced pressure.The residue is purified by chromatography on a column of silica gel witha mixture of solvents (dichloromethane/ethyl acetate: 100/0 to 70/30).The chromatography fractions are partially concentrated. The solid whichprecipitates is collected by filtration, washed with cyclohexane anddried under reduced pressure.

18 g of a white solid formed of methyl 6-fluoro-1H-indole-2-carboxylateare obtained, comprising 10 to 20% of ethyl6-fluoro-1H-indole-2-carboxylate.

1.3. Methyl 6-fluoro-1-methyl-1H-indole-2-carboxylate

A suspension of 7.9 g (197 mmol) of 60% sodium hydride and of 36.1 g(176 mmol) of methyl 6-fluoro-1H-indole-2-carboxylate (obtained in stage1.2.) in 250 ml of N,N-dimethylformamide is stirred for 2 h at ambienttemperature. 12 ml (193 mmol) of iodomethane in 50 ml ofN,N-dimethylformamide are subsequently added. The mixture is stirred atambient temperature for 12 h.

The above reaction medium is poured into a mixture of water and ice.Dichloromethane is added and the aqueous phase is neutralized withhydrochloric acid (1M). The organic phase is separated by settling,washed with water, dried over sodium sulfate, filtered and concentratedunder reduced pressure. The residue is purified by chromatography on acolumn of silica gel with a mixture of solvents(cyclohexane/dichloromethane: 50/50; then dichloromethane/ethyl acetate:100/0 to 70/30).

37.2 g (170 mmol) of a white compound formed of methyl6-fluoro-1-methyl-1H-indole-2-carboxylate are isolated, comprising 10 to20% of ethyl 6-fluoro-1-methyl-1H-indole-2-carboxylate.

1.4. Ethyl6-fluoro-2-(methoxycarbonyl)-1-methyl-α-oxo-1H-indole-3-acetate

A solution of 6.7 ml (60 mmol) of ethyl chlorooxoacetate in 220 ml of1,2-dichloroethane is cooled to 0° C. 6.6 ml (60 mmol) of titaniumtetrachloride are added in small portions. The reaction medium isstirred for 30 min at 0° C. 10 g (47 mmol) of methyl6-fluoro-1-methyl-1H-indole-2-carboxylate (obtained in stage 1.3.) areadded. Stirring is maintained for 12 h at ambient temperature. Themixture is poured into a mixture of water and ice and extracted withdichloromethane. The organic phase is separated by settling, washed withwater, dried over sodium sulfate, filtered and concentrated underreduced pressure. The residue is purified by chromatography on a columnof silica gel with a mixture of solvents (cyclohexane/dichloromethane:50/50; then dichloromethane/ethyl acetate: 100/0 to 90/10). The solid isrecrystallized from a mixture of dichloromethane and ethyl acetate.

12.1 g of yellowish solid formed of ethyl6-fluoro-2-(methoxycarbonyl)-1-methyl-α-oxo-1H-indole-3-acetate areisolated, comprising 10 to 20% of ethyl6-fluoro-2-(ethoxycarbonyl)-1-methyl-α-oxo-1H-indole-3-acetate.

Melting point: 88-91° C.

1.5. Ethyl7-fluoro-5-methyl-4-oxo-3-(pyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxylate

A solution of 0.40 g (1.36 mmol) of ethyl6-fluoro-2-(methoxycarbonyl)-1-methyl-α-oxo-1H-indole-3-acetate(obtained in stage 1.4.) in 30 ml of absolute ethanol, a few drops ofglacial acetic acid and 0.60 g (5.5 mmol) of 2-pyridinylhydrazine isbrought to reflux for 17 h.

The medium is cooled. The insoluble material is collected by filtration,washed with diethyl ether and purified by chromatography on a column ofsilica gel with a mixture of solvents (dichloromethane/ethyl acetate:100/0 to 0/100, then ethyl acetate/methanol: 100/0 to 90/10).

A compound (0.20 g; 0.55 mmol) is isolated in the form of a yellowsolid.

1.6.7-Fluoro-N,N,5-trimethyl-4-oxo-3-(pyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide

A solution of dimethylamine hydrochloride (0.50 g; 6 mmol) in 50 ml oftoluene under argon is cooled to 0° C. and then 4 ml (8 mmol) of atrimethylaluminum solution (2M in toluene) are added in small portions.Stirring is maintained for 2 h at ambient temperature. Ethyl7-fluoro-5-methyl-4-oxo-3-(pyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]-indole-1-carboxylatein the solid form (0.38 g; 1.0 mmol), obtained in stage 1.5., issubsequently added and the reaction medium is heated at 110° C. for 5 h.

The solution is cooled to approximately 0° C. and water is addeddropwise. Dichloromethane and then 30% sodium hydroxide are subsequentlyadded until the aluminum derivatives have been dissolved. The organicphase is separated by settling, washed with water, dried over sodiumsulfate, filtered and concentrated under reduced pressure. The residueis purified by chromatography on a column of silica gel with a mixtureof solvents (dichloromethane/ethyl acetate: 90/10 to 0/100, then ethylacetate/methanol: 100/0 to 90/10). The solid obtained is recrystallizedfrom a mixture of dichloromethane and ethyl acetate.

0.070 g (6.5 mmol) of compound is isolated in the form of a white solid.

Melting point: 199-200° C.

EXAMPLE 2 Compound No. 127-Chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamidehydrochloride (1:1) 2.1. Ethyl7-chloro-5-methyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxylate

A solution of 4.38 g (13.5 mmol) of ethyl6-chloro-2-(ethoxycarbonyl)-1-methyl-α-oxo-1H-indole-3-acetate(disclosed in WO-A-00/44751), of 65 ml of glacial acetic acid and of 2.7ml (55.7 mmol) of hydrazine monohydrate is brought to reflux for 3 h.

The medium is cooled. An insoluble material is collected by filtration,washed with water and dried under reduced pressure.

3.58 g (11.7 mmol) of compound are isolated in the form of a whitesolid.

Melting point: 302-303° C.

2.2.7-Chloro-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide

2.45 g (30 mmol) of dimethylamine hydrochloride in 30 ml of toluene areintroduced under argon. The solution is cooled to 0° C. and then 15 ml(30 mmol) of a trimethylaluminum solution (2M in toluene) are added insmall portions. The reaction medium is stirred for 2 h at ambienttemperature.

30 ml (20.1 mmol) of the solution prepared above are added to asuspension of 2 g (6.5 mmol) of ethyl7-chloro-5-methyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxylate(obtained in stage 2.1.) in 60 ml of toluene. The reaction medium isheated at 100° C. for 3 h.

The solution is cooled to approximately 0° C. and poured into a mixtureof an aqueous hydrochloric acid solution (1M) and ice. The reactionmedium is subsequently basified with an aqueous sodium hydroxidesolution (1M). The precipitate obtained is filtered off, washed withwater and dried under reduced pressure.

A compound (1.99 g; 6.5 mmol) is isolated in the form of a light beigesolid.

Melting point: >300° C.

2.3.7-Chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamidehydrochloride (1:1)

0.4 g of7-chloro-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide(1.3 mmol), obtained in stage 2.2., is dissolved in 35 ml ofN-methylpyrrolidone. 0.21 ml (2.6 mmol) of pyridine, 0.36 ml (2.6 mmol)of triethylamine, 340 mg of molecular sieve, 0.47 g (2.6 mmol) of cupricacetate and 0.42 g (2.6 mmol) of 2-(pyridin-3-yl)-1,3,2-dioxaborinaneare introduced at ambient temperature and under an argon atmosphere.After reacting for 24 h, the insoluble materials are separated byfiltration and 0.21 ml (2.6 mmol) of pyridine, 0.36 ml (2.6 mmol) oftriethylamine, 340 mg of molecular sieve, 0.47 g (2.6 mmol) of cupricacetate and 0.42 g (2.6 mmol) of 2-(pyridin-3-yl)-1,3,2-dioxaborinaneare added to the solution. Stirring is maintained for 24 h. Theinsoluble materials are separated by filtration. The solvent is removedunder reduced pressure. Dichloromethane and water are added to theevaporation residue. The aqueous phase is extracted withdichloromethane. The organic phases are combined, washed with water,dried over sodium sulfate, filtered and concentrated under reducedpressure. The residue is purified by chromatography on a column ofsilica (eluent: heptane/ethyl acetate: 10/90). The white solid obtainedis triturated in diethyl ether. 400 mg of a white solid are isolated.

The hydrochloride is formed by dissolution of the solid isolated abovein ethanol and by addition of a solution of hydrochloric acid (5N) inpropan-2-ol. After recrystallization from propan-2-ol, a compound (0.35g; 0.84 mmol) is isolated in the form of a white solid.

Melting point: 228-230° C.

EXAMPLE 3 Compound No. 47-Fluoro-N,N,5-trimethyl-4-oxo-3-(2-methoxypyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide3.1. Ethyl7-fluoro-5-methyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxylate

A solution of 7.80 g (26.6 mmol) of ethyl6-fluoro-2-(methoxycarbonyl)-1-methyl-α-oxo-1H-indole-3-acetate(obtained in stage 1.4. of Example 1), of 200 ml of glacial acetic acidand of 5 ml (103 mmol) of hydrazine monohydrate is heated at 90° C. for20 h.

The medium is cooled. After addition of water, an insoluble material iscollected by filtration, washed with water and dried under reducedpressure.

5.60 g (19.3 mmol) of compound are isolated in the form of a whitesolid.

Melting point: 314-315° C.

3.2.7-Fluoro-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide

A solution of 2.50 g (30.6 mmol) of dimethylamine hydrochloride in 150ml of toluene, under argon, is cooled to 0° C. and then 18 ml (36 mmol)of a trimethylaluminum solution (2M in toluene) are added in smallportions. Stirring is maintained for 2 h at ambient temperature. 2.6 g(9 mmol) of ethyl7-fluoro-5-methyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxylatein the solid form (obtained in stage 3.1.) are subsequently added. Thereaction medium is heated at 110° C. for 18 h.

The solution is cooled to approximately 0° C. Water and then a 1Mhydrochloric acid solution are added dropwise until a pH of between 1and 2 is obtained. The precipitate is collected by filtration, washedwith water and dried under reduced pressure in the presence ofphosphorus pentoxide.

A compound (1.10 g; 3.8 mmol) is isolated in the form of a white solid.

Melting point: >300° C.

3.3.7-Fluoro-N,N,5-trimethyl-4-oxo-3-(2-methoxy-pyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide

A solution of 0.3 g (1.04 mmol) of7-fluoro-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]-indole-1-carboxamide(obtained in stage 3.2.), 0.120 g (0.63 mmol) of cuprous iodide, 0.20 g(1.45 mmol) of potassium carbonate and 0.60 g (3.19 mmol) of3-bromo-6-methoxypyridine in 50 ml of N,N-dimethylformamide is heated at150° C. for 20 h. The reaction mixture is cooled and concentrated underreduced pressure. Dichloromethane, water and a sodium hydroxide solution(1M) are added. The organic phase is separated by settling, washed withwater, dried over sodium sulfate, filtered and concentrated underreduced pressure. The residue is purified by chromatography on a columnof silica gel (eluent: dichloromethane/ethyl acetate: 100/0 to 0/100;then ethyl acetate/methanol:95/5). The white solid obtained isrecrystallized from a dichloromethane/ethyl acetate mixture and washedwith diethyl ether. A white solid (0.26 g; 0.66 mmol) is isolated.

Melting point: 225-226° C.

EXAMPLE 4 Compound No. 97-Fluoro-N,5-dimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide4.1. Ethyl7-fluoro-5-methyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxylate

Ethyl7-fluoro-5-methyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxylate(0.9 g; 3.11 mmol), obtained in stage 3.1. of Example 3, is dissolved in60 ml of N-methylpyrrolidone. 0.50 ml (6.2 mmol) of pyridine, 0.8 ml(5.7 mmol) of triethylamine, 4 g of molecular sieve, 1.0 g (5.5 mmol) ofcupric acetate and 0.90 g (5.5 mmol) of2-(3-pyridinyl)-1,3,2-dioxaborinane are introduced at ambienttemperature and under an argon atmosphere. After reacting for 24 h, thesolvent is removed under reduced pressure. Dichloromethane, water andsodium hydroxide (1M) are added. The insoluble materials are separatedby filtration, the organic phase is separated by settling and theaqueous phase is extracted with dichloromethane. The organic phases arecombined, washed with water, dried over sodium sulfate, filtered andconcentrated under reduced pressure. The residue is purified bychromatography on a column of silica gel (eluent: dichloromethane/ethylacetate: 100/0 to 0/100; ethyl acetate/methanol: 100/0 to 90/10).

A white solid (0.57 g) is isolated.

Melting point: 214-215° C.

4.2.7-Fluoro-N,5-dimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide

A stream of gaseous methylamine is introduced into a solution of 0.28 g(0.76 mmol) of ethyl7-fluoro-5-methyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxylate(obtained in stage 4.1.) in 30 ml of dichloromethane and 70 ml ofmethanol. Stirring is maintained for 4 h. The reaction medium isconcentrated under reduced pressure. The residue is purified bychromatography on a column of silica gel (eluent:dichloromethane/methanol: 100/0 to 90/10). The solid obtained isrecrystallized from a mixture of dichloromethane and ethyl acetate.

A white solid (0.22 g) is isolated.

Melting point: 270-272° C.

EXAMPLE 5 Compound No. 61-[[7-Fluoro-5-methyl-3-(pyrimidin-2-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]-pyrrolidine5.1.1-[[7-Fluoro-5-methyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidine

12 ml (24 mmol) of a trimethylaluminum solution (2M in toluene) in 100ml of toluene, under argon, are cooled to 0° C. and then 2 ml (24 mmol)of pyrrolidine are added in small portions. Stirring is maintained for 2h at ambient temperature. 2.0 g (6.9 mmol) of ethyl7-fluoro-5-methyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxylate(obtained in stage 3.1. of Example 3) in the solid form are subsequentlyadded. The reaction medium is heated at 110° C. for 18 h.

The solution is cooled to approximately 0° C. Water and then a solutionof hydrochloric acid (1M) are added dropwise until a pH of between 1 and2 is obtained. The precipitate obtained is filtered off, washed withwater and dried under reduced pressure in the presence of phosphoruspentoxide.

A compound (1.50 g; 4.6 mmol) is isolated in the form of a white solid.

Melting point: >300° C.

5.2.1-[[7-Fluoro-5-methyl-3-(pyrimidin-2-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]-pyrrolidine

A solution of 0.24 g (0.73 mmol) of1-[[7-fluoro-5-methyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidine(obtained in stage 5.1.), 0.120 g (0.63 mmol) of cuprous iodide, 0.15 g(1.09 mmol) of potassium carbonate and of 0.30 g (1.89 mmol) of2-bromopyrimidine in 40 ml of N,N-dimethylformamide is heated at 150° C.for 16 h. The reaction mixture is cooled and concentrated under reducedpressure. Dichloromethane, water and a concentrated sodium hydroxidesolution are added. The organic phase is separated by settling, filteredthrough Celite®, washed with water, dried over sodium sulfate, filteredand concentrated under reduced pressure. The residue is purified bychromatography on a column of silica gel (eluent: dichloromethane/ethylacetate: 80/20 to 0/100; ethyl acetate/methanol: 100/0 to 90/10). Thesolid obtained is recrystallized from a dichloromethane/ethyl acetatemixture and washed with diethyl ether.

A white solid (0.04 g; 0.10 mmol) is isolated.

Melting point: 238-239° C.

EXAMPLE 6 Compound No. 264-Methyl-1-[[7-chloro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]-piperazinehydrochloride (1:1) 6.1.4-Methyl-1-[[7-chloro-5-methyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]-piperazine

A solution of 4-methylpiperazine (1.1 ml; 10 mmol) in 10 ml of tolueneis cooled to 0° C. under argon. 5 ml (10 mmol) of a trimethylaluminumsolution (2M in toluene) are added in small portions. Stirring ismaintained for 2 h at ambient temperature. 1.0 g (3.27 mmol) of ethyl7-chloro-5-methyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxylate(obtained in stage 2.1. of Example 2) in 30 ml of toluene issubsequently added. The reaction medium is heated at 110° C. for 2 h.

The solution is cooled to approximately 0° C. Water and then aconcentrated sodium hydroxide solution are added dropwise. Theprecipitate is filtered off, washed with water and dried under reducedpressure in the presence of phosphorus pentoxide.

A compound (0.89 g) is isolated in the form of a white solid.

6.2.4-Methyl-1-[[7-chloro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]piperazinehydrochloride (1:1)

4-Methyl-1-[[7-chloro-5-methyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]-piperazine(0.75 g; 2.1 mmol), obtained in stage 6.1., is dissolved in 60 ml ofN-methylpyrrolidone. 0.39 ml (4.8 mmol) of pyridine, 0.67 ml (4.8 mmol)of triethylamine, 800 mg of molecular sieve, 0.87 g (4.8 mmol) of cupricacetate and 0.78 g (4.8 mmol) of 2-(pyridin-3-yl)-1,3,2-dioxaborinaneare introduced at ambient temperature and under an argon atmosphere.After reacting for 24 h, the insoluble materials are separated byfiltration. 0.39 ml (4.8 mmol) of pyridine, 0.67 ml (4.8 mmol) oftriethylamine, 2.0 g of molecular sieve, 0.87 g (4.8 mmol) of cupricacetate and 0.78 g (4.8 mmol) of 2-(pyridin-3-yl)-1,3,2-dioxaborinaneare added to the solution. Stirring is extended for a further 24 h. Thesolvent is removed under reduced pressure. Dichloromethane and water areadded. The insoluble materials are separated by filtration. The organicphase is separated by settling and the aqueous phase is extracted withdichloromethane. The organic phases are combined, washed with water,dried over sodium sulfate, filtered and concentrated under reducedpressure. The residue is triturated in diisopropyl ether. Theprecipitate obtained is collected by filtration and purified bychromatography on a column of silica gel (eluent:dichloromethane/methanol: 100/0 to 90/10). A cream-colored solid (0.3 g)is isolated.

The hydrochloride is formed by dissolution of the solid in propan-2-oland by addition of 7 ml of a solution of hydrochloric acid (0.1N) inpropan-2-ol. After recrystallization from propan-2-ol, a compound (0.23g; 0.44 mmol) is isolated in the form of a white solid.

Melting point: 267-268° C. (decomposition).

EXAMPLE 7 Compound No. 117-Chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide

0.4 g of7-chloro-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide(1.3 mmol), obtained in stage 2.2. of Example 2, is dissolved in 35 mlof N-methylpyrrolidone. 0.2 ml (2.6 mmol) of pyridine, 0.36 ml (2.6mmol) of triethylamine, 420 mg of molecular sieve, 0.48 g (2.6 mmol) ofcupric acetate and 0.874 g (2.6 mmol) of a mixture [1:1] of lithiumtripropoxypyridin-2-ylboronate and propanol are introduced at ambienttemperature and under an argon atmosphere. After reacting for 24 h, 0.2ml (2.6 mmol) of pyridine, 0.36 ml (2.6 mmol) of triethylamine, 420 mgof molecular sieve, 0.48 g (2.6 mmol) of cupric acetate and 0.874 g (2.6mmol) of a mixture [1:1] of lithium tripropoxypyridin-2-ylboronate andpropanol are added to the solution. Stirring is extended for anadditional 24 h. The solvent is evaporated. Dichloromethane and waterare added. The organic phase is separated by settling and the aqueousphase is extracted with dichloromethane. The organic phases arecombined, dried over sodium sulfate, filtered and concentrated underreduced pressure. The residue is purified by chromatography on a columnof silica gel (eluent: dichloromethane/methanol: 100/0 to 95/5). Thesolid obtained is recrystallized from ethanol.

A light beige solid (0.95 g) is isolated.

Melting point: 210-211° C.

EXAMPLE 8 Compound No. 147-Chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamidehydrochloride (1:1)

0.4 g of7-chloro-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide(1.3 mmol), obtained in stage 2.2. of Example 2, is dissolved in 35 mlof N-methylpyrrolidone. 0.2 ml (2.6 mmol) of pyridine, 0.4 ml (2.7 mmol)of triethylamine, 300 mg of molecular sieve, 0.48 g (2.6 mmol) of cupricacetate and 0.32 g (2.6 mmol) of pyridin-4-ylboronic acid are introducedat ambient temperature and under an argon atmosphere. After reacting for24 h, the insoluble materials are separated by filtration and 0.2 ml(2.6 mmol) of pyridine, 0.4 ml (2.7 mmol) of triethylamine, 300 mg ofmolecular sieve, 0.48 g (2.6 mmol) of cupric acetate and 0.32 g (2.6mmol) of pyridin-4-ylboronic acid are added to the solution. Stirring ismaintained for 24 h. The insoluble materials are separated byfiltration. The solvent is removed under reduced pressure.Dichloromethane and water are added to the evaporation residue. Theaqueous phase is extracted with dichloromethane. The organic phases arecombined, washed with water, dried over sodium sulfate, filtered andconcentrated under reduced pressure. The residue is purified bychromatography on a column of silica gel (eluent: cyclohexane/ethylacetate: 10/90, then dichloromethane/methanol: 95/5). The white solidobtained is triturated in diethyl ether. 350 mg of7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide(Compound No. 13) are isolated in the form of a white solid.

Melting point: 276-278° C.

The hydrochloride is formed by dissolution of the solid isolated abovein ethanol and by addition of a solution of hydrochloric acid (5N) inpropan-2-ol. After recrystallization from propan-2-ol, a compound (0.30g; 0.72 mmol) is isolated in the form of a white solid.

Melting point: 263-265° C.

EXAMPLE 9 Compound No. 377-Chloro-N,N,5-trimethyl-3-(oxidopyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide

0.35 g (0.92 mmol) of7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,obtained in Example 8, is dissolved in 30 ml of glacial acetic acid. 3.5g (36 mmol) of a hydrogen peroxide solution (35% in water) are slowlyadded. The reaction mixture is heated at 80° C. for 30 h and then cooledto ambient temperature. Water and then sodium hydrogencarbonate areadded until a pH of approximately 8 is obtained. The aqueous phase isextracted with dichloromethane. The organic phase is washed with water,dried over sodium sulfate, filtered and concentrated under reducedpressure. The residue is purified by chromatography on a column ofsilica gel (eluent: dichloromethane/methanol: 98/2 to 80/20). The solidobtained is recrystallized from methanol. 100 mg of compound areobtained in the form of a white solid.

Melting point: 301-304° C.

EXAMPLE 10 Compound No. 387-Chloro-3-(2-methoxypyridin-4-yl)-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide10.1.3-(2-Bromopyridin-4-yl)-7-chloro-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide

0.34 g (0.85 mmol) of7-chloro-N,N,5-trimethyl-3-(1-oxidopyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,obtained in Example 9, is dissolved in 50 ml of dichloromethane under aninert atmosphere. 0.24 ml (1.7 mmol) of triethylamine is added. Themixture is cooled with a bath of ice-cold water and 0.49 g (1.7 mmol) ofphosphorus oxybromide is added in small portions. The reaction medium isstirred for 30 minutes at ambient temperature, then heated for 2 h 30 atreflux and, finally, cooled to ambient temperature. It is subsequentlypoured onto crushed ice. Dichloromethane and an aqueous sodium hydroxidesolution (1M) are added until a basic pH is reached. The organic phaseis separated by settling, washed with water, dried over sodium sulfate,filtered and concentrated under reduced pressure. The residue ispurified by chromatography on a column of silica gel (eluent:dichloromethane/ethyl acetate: 80/20 to 0/100). 180 mg of a white solidare isolated. This compound is used as is in the following stage.

10.2.7-Chloro-3-(2-methoxypyridin-4-yl)-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide

120 mg (5.2 mmol) of sodium are added under an inert atmosphere to 20 mlof methanol. 180 mg (0.39 mmol) of3-(2-bromopyridin-4-yl)-7-chloro-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,obtained in Example 10.1., and 20 ml of N,N-dimethylformamide are added.The solution is heated at 80° C. for 14 h. It is cooled to ambienttemperature and then concentrated under reduced pressure. Water anddichloromethane are added to the residue. The organic phase is separatedby settling, washed with water, dried over sodium sulfate, filtered andconcentrated under reduced pressure. The residue is purified bychromatography on a column of silica gel (eluent: dichloromethane/ethylacetate: 80/20 to 0/100). The solid obtained is recrystallized from adichloromethane/ethyl acetate mixture and then rinsed with diethylether. 60 mg of a white solid are isolated.

Melting point: 237-238° C.

The chemical structures and the physical properties of some compounds ofthe invention are illustrated in the following table.

In the “Salt” column of this table, “HCl” denotes a hydrochloride and“-” denotes a compound in the form of the base. The acid:base molarratios are indicated opposite.

TABLE (I)

Compound No. X R₁ NR₂R₃ Het Salt M.p. (° C.) 1 F CH₃ N(CH₃)₂pyridin-2-yl — 199-200 2 F CH₃ N(CH₃)₂ pyridin-3-yl — 220-221 3 F CH₃N(CH₃)₂ pyridin-4-yl HCl 1:1 266-271 4 F CH₃ N(CH₃)₂2-methoxypyridin-5-yl — 225-226 5 F CH₃ N(CH₃)₂ quinolin-3-yl — 237-2386 F CH₃

pyrimidin-2-yl — 238-239 7 F CH₃

pyridin-3-yl HCl 1:1 269-273 8 F CH₃

pyridin-3-yl — 220-221 9 F CH₃ NH(CH₃) pyridin-3-yl — 270-272 10 F CH₃NH₂ pyridin-3-yl — 319-320 11 Cl CH₃ N(CH₃)₂ pyridin-2-yl — 210-211 12Cl CH₃ N(CH₃)₂ pyridin-3-yl HCl 1:1 228-230 13 Cl CH₃ N(CH₃)₂pyridin-4-yl — 276-278 14 Cl CH₃ N(CH₃)₂ pyridin-4-yl HCl 1:1 263-265 15Cl CH₃ N(CH₃)₂ 5-methylpyridin-2-yl — 222-224 16 Cl CH₃ N(CH₃)₂2-methoxypyridin-5-yl — 236-237 17 Cl CH₃ N(CH₃)₂ 2-methylpyridin-5-yl —214-216 18 Cl CH₃ N(CH₃)₂ 2-bromopyridin-5-yl — 250-252 19 Cl CH₃N(CH₃)₂ quinolin-3-yl — 271-272 20 Cl CH₃ N(CH₃)₂ isoquinolin-4-yl —189-191 21 Cl CH₃ N(CH₃)₂ 6-methylpyridazin-3-yl — 238-239 22 Cl CH₃N(CH₃)₂ pyrimidin-5-yl — 251-252 23 Cl CH₃ N(CH₃)₂ pyrimidin-2-yl —272-274 24 Cl CH₃ N(CH₃)₂ pyrazin-2-yl — 231-232 25 Cl CH₃

pyridin-3-yl HCl 1:1 232-234 26 Cl CH₃

pyridin-3-yl HCl 1:1 267-268 27 Cl CH₃

pyridin-4-yl — 236-237 28 Cl CH₃ NH(CH₃) pyridin-4-yl — 321-323 29 ClCH₃ NH₂ pyridin-4-yl — 341-346 30 Cl CH₃ N(CH₃)₂ 4-methoxypyridin-2-yl —243-244 31 Cl CH₃

pyridin-4-yl — 307-308 32 Cl CH₃ N(CH₂CH₃)₂ pyridin-4-yl — 217-218 33 ClCH₃ NCH₃(CH₂CH₃) pyridin-4-yl — 211-213 34 Cl CH₃

pyridin-4-yl — 242-243 35 Cl CH₃ N(CH₃)₂ 2-methylpyridin-4-yl — 267-26936 Cl CH₃

2-methylpyridin-4-yl — 246-247 37 Cl CH₃ N(CH₃)₂ 1-oxidopyridin-4-yl —301-304 38 Cl CH₃ N(CH₃)₂ 2-methoxypyridin-4-yl — 237-238

The compounds of the invention have been subjected to pharmacologicaltests which have demonstrated their advantage as substances withtherapeutic activities.

The compounds of the invention also exhibit characteristics ofsolubility in water which promote good in vivo activity.

Study of the Binding of [³H]Ro5-4864 to Peripheral-Type BenzodiazepineReceptors (PBR or p Sites)

The affinity of the compounds of the invention for PBR or p sites (sitesof binding of peripheral type to benzodiazepines) was determined.

The p site receptors can be labeled selectively in rat kidney membranesincubated in the presence of [³H]Ro5-4864. The compounds of theinvention have formed the subject of an in vitro study with respect totheir affinity for these receptors.

The animals used are male Sprague-Dawley rats (Iffa Credo) weighing 180to 300 g. After decapitation, the kidney is removed and the tissue ishomogenized at 4° C. using a Polytron homogenizer for 2 min at 6/10 ofthe maximum speed in 35 volumes of 50 mM Na₂HPO₄ phosphate buffer at apH adjusted to 7.5 with NaH₂PO₄. The membrane homogenate is filteredthrough gauze and diluted tenfold with buffer.

[³H]Ro5-4864 (specific activity: 70-90 Ci/mmol; New England Nuclear), ata concentration of 0.5 nM, is incubated in the presence of 100 μl of themembrane homogenate in a final volume of 1 ml of buffer comprising thetest compound.

After incubating for 3 h at 0° C., the membranes are recovered byfiltration through Whatman GF/B™ filters washed with 2 times 4.5 ml ofcold (0° C.) incubation buffer. The amount of radioactivity retained bythe filter is measured by liquid scintigraphy.

For each concentration of studied compound, the percentage of inhibitionof the binding of [³H]Ro5-4864 is determined and then the IC₅₀concentration, the concentration which inhibits 50% of the specificbinding, is determined.

The IC₅₀ values of the most active compounds of the invention range from1 nM to 200 nM.

The compounds of the invention are therefore ligands with an affinityfor peripheral-type benzodiazepine receptors.

Study of the Neurotrophic Activity

Test of Survival of the Motor Neurons After Sectioning the Facial Nervein Rats Aged 4 Days

After lesion of the facial nerve in immature rats, the motor neurons ofthe facial nucleus experience neuronal death by apoptosis. Neuronalsurvival is evaluated using neuronal counting and histological methods.

Immature rats aged 4 days are anaesthetized with pentobarbital (3 mg/kgby the i.p. route). The right facial nerve is exposed and sectioned atits outlet from the stylomastoid foramen. After waking up, the youngrats are returned to their mothers and are treated for 7 days with oneor two daily administrations, by the oral or intraperitoneal route, atdoses ranging from 1 to 10 mg/kg.

7 days after the lesion, the animals are decapitated and the brains arefrozen in isopentane at −40° C. The entire facial nerve is cut with acryostat into sections with a width of 10 μm. The motor neurons arestained with cresyl violet and counted using the Histo™ software(Biocom™).

In this model, the compounds of the invention increase neuronal survivalby approximately 10 to 30%.

The results of the tests show that the most active compounds of theinvention promote nerve regeneration.

The compounds of the invention can therefore participate in thecomposition of a medicament.

They can be used for the preparation of medicaments intended for theprevention and/or treatment of various types of peripheral neuropathies,such as traumatic or ischaemic neuropathies, infectious, alcoholic,medicinal or genetic neuropathies, and motor neuron conditions, such asspinal amyotrophies and amyotrophic lateral sclerosis. These medicamentswill also find an application in the treatment of neurodegenerativediseases of the central nervous system, either of acute type, such asstrokes and cranial and medullar traumas, or of chronic type, such asautoimmune diseases (multiple sclerosis), Alzheimer's disease,Parkinson's disease and any other disease in which the administration ofneurotrophic factors is supposed to have a therapeutic effect.

The compounds of the invention can also be used for the preparation ofmedicaments intended for the prevention and/or treatment of anxiety, ofepilepsy and of sleep disorders. This is because ligands of the PBR or psites stimulate the production of neurosteroids, such as pregnenolone,dehydroeplandrosterone and 3α-hydroxy-5α-pregnan-20-one, by promotingthe transfer of cholesterol from the outside to the inside of themitochondrial membrane. These neurosteroids modulate the activity of theGABA_(A)-chloride channel macromolecular complex and can thus produceanxiolytic, anticonvulsant and sedative activities (D. Bitran et al.,Psychopharmacology, 2000, 151, 64-71; S. Okuyama et al., Life Sci.,1999, 64 (16), 1455-1464; L. D. McCauley et al., Eur. J. Pharmacol.,1995, 276, 145-153; S. K. Kulkarni et al., Drugs of Today, 1995, 31,433-4558).

The compounds of the invention can also be used in the treatment ofacute or chronic renal insufficiency, of glomerulonephritis, of diabeticnephropathy, of cardiac ischaemia and cardiac insufficiency, ofmyocardial infarction, of ischaemia of the lower limbs, of coronaryvasospasm, of angina pectoris, of pathologies associated with the heartvalves, of inflammatory heart diseases, of side effects due tocardiotoxic medicaments or as a result of heart surgery, ofatherosclerosis and of its thromboembolic complications, of restenosis,of graft rejections, or of conditions related to incorrect proliferationor incorrect migration of smooth muscle cells.

Furthermore, recent data in the literature indicate that theperipheral-type benzodiazepine receptor might play a fundamental role inthe regulation of cell proliferation and cancerization processes.Generally, and in comparison with normal tissues, an increased densityof peripheral-type benzodiazepine receptors is observed in various typesof tumors and cancers.

In human astrocytomas, the level of expression of the peripheral-typebenzodiazepine receptor is correlated with the degree of malignancy ofthe tumor, the proliferation index and the survival of the patients. Inhuman cerebral tumors, the increase in the number of peripheral-typebenzodiazepine receptors is used as a diagnostic indication in medicalimaging and as a therapeutic target for conjugates formed from a ligandof the peripheral-type benzodiazepine receptor and from a cytostaticdrug. A high density of peripheral-type benzodiazepine receptors is alsoobserved in ovarian carcinomas and breast cancers. As regards thelatter, it has been demonstrated that the level of expression of theperipheral-type benzodiazepine receptors is related to the aggressivepotential of the tumor; furthermore, the presence of a peripheral-typebenzodiazepine receptor agonist stimulates the growth of a mammarycancer line.

These combined results, which suggest a deleterious function of theperipheral-type benzodiazepine receptor in cancerization processes,constitute a relevant basis for the search for synthetic ligandsspecific for the peripheral-type benzodiazepine receptor which arecapable of blocking the effects thereof.

The compounds can therefore be used for the treatment of tumors andcancers.

The peripheral-type benzodiazepine receptors are also present in theskin and, in this respect, the compounds which can be used according tothe invention can be used for the prophylaxis or the treatment ofcutaneous stress.

The term “cutaneous stress” is understood to mean the various situationswhich might cause damage, in particular to the epidermis, whatever theagent which causes this stress. This agent can be internal and/orexternal to the body, such as a chemical or free-radical agent, or elseexternal, such as ultraviolet radiation.

Thus, the compounds which can be used according to the invention areintended to prevent and to combat cutaneous irritation, dry patches,erythemas, dysaesthetic sensations, heating sensations, pruritus of theskin and/or mucous membranes, or ageing, and can also be used incutaneous disorders, such as, for example, psoriasis, pruriginousdiseases, herpes, photodermatoses, atopic dermatitides, contactdermatitides, lichens, prurigo, pruritus, insect stings, in fibroses andother disorders of collagen maturation, in immunological disorders or indermatological conditions, such as eczema.

The compounds of the invention can also be used for the prevention andtreatment of chronic inflammatory diseases, in particular rheumatoidarthritis, and pulmonary inflammatory diseases, in particular asthma,acute respiratory distress syndrome (ARDS) and chronic obstructivepulmonary diseases (COPD), cystic fibrosis, bronchopulmonary diseases,lung diseases or pulmonary fibrosis.

Thus, a subject-matter of the invention is pharmaceutical compositionscomprising an effective dose of at least one compound of general formula(I), in the form of the base, of a pharmaceutically acceptable salt, ofa pharmaceutically acceptable solvate or of a pharmaceuticallyacceptable hydrate, as a mixture, if appropriate, with suitableexcipients.

The said excipients are chosen according to the pharmaceutical form andthe method of administration desired.

The pharmaceutical compositions of the invention may thus be intendedfor oral, sublingual, subcutaneous, intramuscular, intravenous, topical,intratracheal, intranasal, transdermal, rectal or intraocularadministration.

The unit administration forms can be, for example, tablets, gelatincapsules, granules, powders, solutions or suspensions to be taken orallyor to be injected, transdermal patches or suppositories. Ointments,lotions and collyria can be envisaged for topical administration.

The said unit forms are dosed to allow a daily administration of 0.001to 20 mg of active principle per kg of body weight, according to thepharmaceutical dosage form.

To prepare tablets, a pharmaceutical vehicle, which can be composed ofdiluents, such as, for example, lactose, microcrystalline cellulose orstarch, and formulation adjuvants, such as binders(polyvinylpyrrolidone, hydroxypropylmethylcellulose, and the like), flowagents, such as silica, or lubricants, such as magnesium stearate,stearic acid, glyceryl tribehenate or sodium stearylfumarate, is addedto the micronized or unmicronized active principle. Wetting orsurface-active agents, such as sodium lauryl sulfate, can also be added.

The preparation techniques can be direct tableting, dry granulation, wetgranulation or hot melt.

The tablets can be bare, coated with sugar, for example with sucrose, orcoated with various polymers or other appropriate materials. They can bedesigned to make possible rapid, delayed or sustained release of theactive principle by virtue of polymer matrices or of specific polymersused in the coating.

To prepare gelatin capsules, the active principle is mixed with drypharmaceutical vehicles (simple mixing, dry or wet granulation, or hotmelt) or liquid or semisolid pharmaceutical vehicles.

The gelatin capsules can be hard or soft and coated or uncoated with athin film, so as to have a rapid, sustained or delayed activity (forexample, for an enteric form).

A composition in the form of a syrup or an elixir or for administrationin the form of drops can comprise the active principle in conjunctionwith a sweetener, preferably a calorie-free sweetener, methylparaben orpropylparaben, as antiseptic, a flavor enhancer and a colorant.

The water-dispersible powders and granules can comprise the activeprinciple as a mixture with dispersing agents or wetting agents, ordispersing agents, such as polyvinylpyrrolidone, as well as withsweeteners and flavor-correcting agents.

Recourse is had, for rectal administration, to suppositories preparedwith binders which melt at the rectal temperature, for example cocoabutter or polyethylene glycols.

Use is made, for parenteral administration, of aqueous suspensions,isotonic saline solutions or sterile solutions which are injectablecomprising pharmacologically compatible dispersing agents and/or wettingagents, for example propylene glycol or butylene glycol.

The active principle can also be formulated in the form ofmicrocapsules, optionally with one or more carriers or additives, orelse with a polymer matrix or with a cyclodextrin (transdermal patchesor sustained release forms).

The topical compositions according to the invention comprise a mediumcompatible with the skin. They can be provided in particular in the formof aqueous, alcoholic or aqueous/alcoholic solutions, of gels, ofwater-in-oil or oil-in-water emulsions having the appearance of a creamor of a gel, of microemulsions or of aerosols or in the form ofvesicular dispersions comprising ionic and/or nonionic lipids. Thesepharmaceutical dosage forms are prepared according to methodsconventional in the fields under consideration.

1. A method for the treatment of a pathology in which the peripheralbenzodiazepine receptors are involved which comprises administering to apatient in need of said treatment a therapeutically effective amount ofa compound of formula (I):

wherein X represents a hydrogen or halogen atom, R₁ represents ahydrogen atom or a (C₁-C₄)alkyl group, R₂ and R₃ each represent,independently of one another, a hydrogen atom or a (C₁-C₄)alkyl group orelse R₂ and R₃ form, with the nitrogen atom which carries them, apyrrolidinyl, piperidinyl, morpholinyl or 4-alkylpiperazinyl group, andHet represents a heteroaryl group selected from pyridinyl,1-oxidopyridinyl, quinolinyl, isoquinolinyl, pyrimidinyl, pyrazinyl andpyridazinyl, optionally substituted with one or more halogen atomsand/or one or more (C₁-C₄)alkyl or (C₁-C₄)alkoxy groups, or a hydrate oracid addition salt thereof; and wherein said pathology is selected fromthe group consisting of peripheral neuropathy, motor neuron condition,neurodegenerative disease of the central nervous system, anxiety,epilepsy, sleep disorder, acute or chronic renal insufficiency,glomerulonephritis, diabetic nephropathy, cardiac ischaemia and cardiacinsufficiency, myocardial infarction, ischaemia of the lower limbs,coronary vasospasm, angina pectoris, pathologies associated with theheart valves, inflammatory heart disease, side effects due tocardiotoxic medicaments or as a result of heart surgery, atherosclerosisand its thromboembolic complications, restenosis, graft rejection,conditions related to incorrect proliferation or incorrect migration ofsmooth muscle cells, cancer, cutaneous stress, chronic inflammatorydisease and pulmonary inflammatory disease.
 2. A method for thetreatment of a pathology in which the peripheral benzodiazepinereceptors are involved which comprises administering to a patient inneed of said treatment a therapeutically effective amount of a compoundof formula (I):

wherein X represents a hydrogen or halogen atom, R₁ represents ahydrogen atom or a (C₁-C₄)alkyl group, R₂ and R₃ each represent,independently of one another, a hydrogen atom or a (C₁-C₄)alkyl group orelse R₂ and R₃ form, with the nitrogen atom which carries them, apyrrolidinyl, piperidinyl, morpholinyl or 4-alkylpiperazinyl group, andHet represents a heteroaryl group selected from pyridinyl,1-oxidopyridinyl, quinolinyl, isoquinolinyl, pyrimidinyl, pyrazinyl andpyridazinyl, optionally substituted with one or more halogen atomsand/or one or more (C₁-C₄)alkyl or (C₁-C₄)alkoxy groups, or a hydrate oracid addition salt thereof; and wherein said pathology is selected fromthe group consisting of peripheral neuropathy; spinal amyotrophy;amyotrophic lateral sclerosis; stroke; cranial and medullar trauma;multiple sclerosis; Alzheimer's disease; Parkinson's disease; anxiety;epilepsy, sleep disorder and diabetic nephropathy.
 3. The method as setforth in claim 2 wherein X represents a halogen atom; R₁ represents a(C₁-C₄)alkyl; R₂ and R₃ each represent, independently of one another, ahydrogen atom or a (C₁-C₄)alkyl group, or else R₂ and R₃ form, with thenitrogen atom which carries them, a pyrrolidinyl, piperidinyl,morpholinyl or 4-alkylpiperazinyl group; Het represents a heteroarylgroup selected from pyridinyl, quinolinyl, isoquinolinyl, pyrimidinyl,pyrazinyl and pyridazinyl, optionally substituted with one or morehalogen atoms, and/or one or more (C₁-C₄)alkyl groups or (C₁-C₄)alkoxygroups.
 4. The method as set forth in claim 2 wherein the compound isselected from the group consisting of:7-fluoro-N,N,5-trimethyl-4-oxo-3-(pyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-fluoro-N,N,5-trimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-fluoro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamidehydrochloride (1:1),7-fluoro-N,N,5-trimethyl-4-oxo-3-(2-methoxypyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-fluoro-N,N,5-trimethyl-4-oxo-3-(quinolin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,1-[[7-fluoro-5-methyl-3-(pyrimidin-2-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidine,4-methyl-1-[[7-fluoro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]piperazinehydrochloride (1:1),1-[[7-fluoro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidine,7-fluoro-N,5-dimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-fluoro-5-methyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamidehydrochloride (1:1),7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamidehydrochloride (1:1),7-chloro-N,N,5-trimethyl-4-oxo-3-(5-methylpyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methoxypyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methylpyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(2-bromopyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(quinolin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(isoquinolin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(6-methyl-pyridazin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyrimidin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyrimidin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyrazin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,1-[[7-chloro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidinehydrochloride (1:1),4-methyl-1-[[7-chloro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]piperazinehydrochloride (1:1),1-[[7-chloro-5-methyl-3-(pyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidine,7-chloro-N,5-dimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-5-methyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(4-methoxypyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,1-[[7-chloro-5-methyl-3-(pyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]morpholine,7-chloro-N,N,-diethyl-5-methyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N-ethyl-N,5-dimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,1-[[7-chloro-5-methyl-3-(pyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]piperidine,7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methylpyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,1-[[7-chloro-5-methyl-3-(2-methylpyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidine,7-chloro-N,N,5-trimethyl-3-(1-oxidopyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-3-(2-methoxypyridin-4-yl)-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,and3-(2-bromopyridin-4-yl)-7-chloro-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,or a pharmaceutically acceptable salt or a hydrate thereof.
 5. Themethod as set forth in claim 2 wherein the compound is selected from thegroup consisting of:7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methoxypyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methylpyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,and7-chloro-N,N,5-trimethyl-4-oxo-3-(2-bromopyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,or a pharmaceutically acceptable salt or a hydrate thereof.
 6. Themethod as set forth in claim 2 wherein said pathology is peripheralneuropathy.
 7. The method as set forth in claim 6 wherein saidperipheral neuropathy is selected from the group consisting of traumaticor ischaemic neuropathy and infectious, alcoholic, medicinal or geneticneuropathy.
 8. A method for the treatment of a disease comprisingadministering to a patient in need of said treatment a therapeuticallyeffective amount of a compound of formula (I):

wherein X represents a hydrogen or halogen atom, R₁ represents ahydrogen atom or a (C₁-C₄)alkyl group, R₂ and R₃ each represent,independently of one another, a hydrogen atom or a (C₁-C₄)alkyl group orelse R₂ and R₃ form, with the nitrogen atom which carries them, apyrrolidinyl, piperidinyl, morpholinyl or 4-alkylpiperazinyl group, andHet represents a heteroaryl group selected from pyridinyl,1-oxidopyridinyl, quinolinyl, isoquinolinyl, pyrimidinyl, pyrazinyl andpyridazinyl, optionally substituted with one or more halogen atomsand/or one or more (C₁-C₄)alkyl or (C₁-C₄)alkoxy groups, or a hydrate oracid addition salt thereof; and wherein said disease is selected fromthe group consisting of peripheral neuropathy; spinal amyotrophy;amyotrophic lateral sclerosis; stroke; cranial and medullar trauma;multiple sclerosis; Alzheimer's disease; Parkinson's disease; anxiety;epilepsy, sleep disorder and diabetic nephropathy.
 9. The method as setforth in claim 8 wherein X represents a halogen atom; R₁ represents a(C₁-C₄)alkyl; R₂ and R₃ each represent, independently of one another, ahydrogen atom or a (C₁-C₄)alkyl group, or else R₂ and R₃ form, with thenitrogen atom which carries them, a pyrrolidinyl, piperidinyl,morpholinyl or 4-alkylpiperazinyl group; Het represents a heteroarylgroup selected from pyridinyl, quinolinyl, isoquinolinyl, pyrimidinyl,pyrazinyl and pyridazinyl, optionally substituted with one or morehalogen atoms, and/or one or more (C₁-C₄)alkyl groups or (C₁-C₄)alkoxygroups.
 10. The method as set forth in claim 8 wherein the compound isselected from the group consisting of:7-fluoro-N,N,5-trimethyl-4-oxo-3-(pyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-fluoro-N,N,5-trimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-fluoro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamidehydrochloride (1:1),7-fluoro-N,N,5-trimethyl-4-oxo-3-(2-methoxypyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-fluoro-N,N,5-trimethyl-4-oxo-3-(quinolin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,1-[[7-fluoro-5-methyl-3-(pyrimidin-2-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidine,4-methyl-1-[[7-fluoro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]piperazinehydrochloride (1:1),1-[[7-fluoro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidine,7-fluoro-N,5-dimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-fluoro-5-methyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamidehydrochloride (1:1),7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamidehydrochloride (1:1),7-chloro-N,N,5-trimethyl-4-oxo-3-(5-methylpyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methoxypyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methylpyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(2-bromopyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(quinolin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(isoquinolin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(6-methyl-pyridazin-3-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyrimidin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyrimidin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(pyrazin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,1-[[7-chloro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidinehydrochloride (1:1),4-methyl-1-[[7-chloro-5-methyl-3-(pyridin-3-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]piperazinehydrochloride (1:1),1-[[7-chloro-5-methyl-3-(pyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidine,7-chloro-N,5-dimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-5-methyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(4-methoxypyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,1-[[7-chloro-5-methyl-3-(pyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]morpholine,7-chloro-N,N,diethyl-5-methyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N-ethyl-N,5-dimethyl-4-oxo-3-(pyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,1-[[7-chloro-5-methyl-3-(pyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]piperidine,7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methylpyridin-4-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,1-[[7-chloro-5-methyl-3-(2-methylpyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indol-1-yl]carbonyl]pyrrolidine,7-chloro-N,N,5-trimethyl-3-(1-oxidopyridin-4-yl)-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-3-(2-methoxypyridin-4-yl)-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,and3-(2-bromopyridin-4-yl)-7-chloro-N,N,5-trimethyl-4-oxo-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,or a pharmaceutically acceptable salt or a hydrate thereof.
 11. Themethod as set forth in claim 8 wherein the compound is selected from thegroup consisting of:7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methoxypyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,7-chloro-N,N,5-trimethyl-4-oxo-3-(2-methylpyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,and7-chloro-N,N,5-trimethyl-4-oxo-3-(2-bromopyridin-5-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-carboxamide,or a pharmaceutically acceptable salt or a hydrate thereof.
 12. Themethod as set forth in claim 8 wherein said disease is peripheralneuropathy.
 13. The method as set forth in claim 12 wherein saidperipheral neuropathy is selected from the group consisting of traumaticor ischaemic neuropathy and infectious, alcoholic, medicinal or geneticneuropathy.
 14. The method as set forth in claim 12 wherein saidperipheral neuropathy is traumatic or ischaemic neuropathy.
 15. Themethod as set forth in claim 12 wherein said peripheral neuropathy isinfectious, alcoholic, medicinal or genetic neuropathy.
 16. The methodas set forth in claim 12 wherein said peripheral neuropathy isinfectious neuropathy.
 17. The method as set forth in claim 12 whereinsaid peripheral neuropathy is medicinal neuropathy.
 18. The method asset forth in claim 12 wherein said peripheral neuropathy is geneticneuropathy.
 19. The method as set forth in claim 8 wherein said diseaseis diabetic nephropathy.